Cochliobolus sativus (Anamorph: Bipolaris sorokiniana) causes several important diseases, including spot blotch, black point and common root rot, in barley and wheat. The fungus produces typical necrosis and chlorosis on leaves of susceptible barley hosts and therefore host-selective toxins (HSTs) are hypothesized to be involved in the virulence. Our recent study suggested that non-ribosomal peptide synthetases are required for the biosynthesis of HSTs in C. sativus. However, the global regulation of biosynthesis of the HSTs or secondary metabolites is not well understood in this fungus. Recently, the velvet complex containing LaeA, VeA, and VelB have been shown to be involved in global regulation of secondary metabolism and/or fungal development in Aspergillus nidulans and several other fungal pathogens. To characterize the function of a velvet-like complex in C. sativus, orthologues of the three component genes (CsVeA, CsVelB and CsLaeA,) were identified and deletion mutants (ΔCsVeA, ΔCsVelB and ΔCsLaeA,) were generated. The ΔCsVeA, ΔCsVelB and ΔCsLaeA mutants showed smaller conidia and less aerial mycelia on PDA compared to the wild type strain. Virulence tests on barley plants indicated that the ΔCsVeA and ΔCsVelB strains were significantly reduced in virulence while the virulence of the ΔCsLaeA strains was slightly reduced as compared to the wild type. To understand the interactions of these velvet complex components, double gene deletion mutants (ΔCsLaeA+ΔCsVelB, ΔCsLaeA+ΔCsVeA and ΔCsVelB+ΔCsVeA) were also generated. These mutants are being characterized and the results will be presented.